5 Colo. Code Regs. § 1002-38.101
The provisions of C.R.S. 25-8-202(1)(a), (b) and (2); 25-8-203; 25-8-204; and 25-8-402; provide the specific statutory authority for adoption of these regulatory amendments. The commission also adopted in compliance with 24-4-103(4) C.R.S. the following statement of basis and purpose.
BASIS AND PURPOSE
Some segments were renumbered, combined, or new segments were created to facilitate appropriate organization of water bodies in this regulation. Renumbering and/or creation of new segments was made based on information that showed:
Upper South Platte segments 2b and 2c (COSPUS02b and COSPUS02c): The portion of Mosquito Creek from the confluence with South Mosquito Creek to Road #698 (39.270971, 106.098846) was moved from Segment 2b to Segment 2c. This move facilitated removal of the Water Supply use from Segment 2c, which now includes South Mosquito Creek, No Name Creek, and the portion of Mosquito Creek from South Mosquito Creek to Road #698. The Water Supply use was retained on Segment 2b, which includes the portion of Mosquito Creek from Road #698 to the Middle Fork of the South Platte River.
Cherry Creek segments 5 and 7 (COSPCH05 and COSPCH07): Rueter-Hess Reservoir was moved from Segment 5 to new Segment 7 to facilitate adoption of a Class 1 Aquatic Life use classification based on the presence of a diverse fish community. Parker Water stated that it may seek removal of the Agricultural use classification from Segment 7 in a future hearing if evidence shows that there is no existing or reasonably expected agricultural use of water stored in the reservoir. A Direct Use Water Supply sub-classification was added to recognize the conveyance of raw water to a treatment facility. Parker Water provided information clarifying that the source water for Rueter-Hess Reservoir is diverted from Cherry Creek below a qualified discharger which means that application of interim numeric nutrient standards is not appropriate at this time, and expressed an interest in working with stakeholders to develop site-specific nutrient standards. As part of this change, an exception for Segment 7 was added to the segment description for Segment 5.
Clear Creek segments 12a and 12b (COSPCL12a and COSPCL12b): The portion of Beaver Brook from Highway 40 to the confluence with Soda Creek, and the mainstem of Soda Creek from the source to the confluence with Clear Creek, were moved from Segment 12a to Segment 12b. Segment 12b previously contained only the portion of Beaver Brook from the source to Highway 40 and is classified as Aquatic Life Cold 1 with CS-I temperature standards. The move facilitated changing the Aquatic Life use (from Cold 2 to Cold 1) and the temperature standards (from CS-II to CS-I) based on presence of brook trout in these water bodies.
St. Vrain Segment 6 (COSPSV06): Segment 6 was resegmented into 6a and 6b to recognize the presence of existing and potential future Water Supply use in a portion of the parent segment. Segment 6a includes the portion of Dry Creek and tributaries from the source to the inlet of Boulder Reservoir and Segment 6b retained the rest of the stream portions from the parent segment. This resegmentation facilitated the adoption of the Water Supply use classification for Segment 6b.
Big Dry Creek Segment 5 (COSPBD05): Lakes and reservoirs from Segment 5 were moved into new Segment 5b. This was to be consistent with the convention of keeping lakes and reservoirs in separate segments from streams. Segment 5a retained the stream portions from the parent segment. As part of this change, an exception for Segment 5a was added to the segment description for Segment 4a and an exception for Segment 5b was added to the segment description for Segment 7.
Big Thompson segments 2, 3, 4a, 4b, 4c, and 7 (COSPBT02, COSPBT03, COSPBT04a, COSPBT04b, COSPBT04c, COSPBT07): Segments 2, 3, and 4a were combined into Segment 2, as the uses and standards are the same for all three segments as a result of upgrades to the Aquatic Life use (from Cold 2 to Cold 1) on Segment 3 and Recreation use (from seasonal N/E to year-round E) on Segment 4a. From Segment 2, the exception of Segment 7 was deleted, which resulted in moving the mainstem of the North Fork of the Big Thompson River from the Rocky Mountain National Park boundary to the confluence with the Big Thompson River to Segment 2 (the uses and standards are the same for segments 2 and 7). From Segment 2, the references to Black Canyon Creek and Glacier Creek below Estes Park water treatment plant were deleted, as this portion of these waters is outside of the Rocky Mountain National Park boundary and is in Segment 2 by default. To minimize the number of deleted segments retained as placeholders, Segment 4a was deleted, Segment 4b was renamed Segment 3, and Segment 4c was renamed Segment 4; segments 4b and 4c were then also deleted. The result of all changes combined is that waters previously in segments 2, 3, 4a, 4b, 4c, and 7 now occupy segments 2, 3, 4, and 7.
Cache la Poudre segments 2b and 3 (COSPCP02b and COSPCP03): Elkhorn Creek, including its tributaries and wetlands, from the source to a point immediately above the confluence with Manhattan Creek, was moved from Segment 2b to Segment 3. The move facilitated changing the temperature standards from CS-II to CS-I based on presence of brook trout in Elkhorn Creek and its tributaries above Manhattan Creek. As part of this change, an exception for Segment 3 was added to the segment description for Segment 2b.
Cache la Poudre segments 7, 8, and 9 (COSPCP07, COSPCP08, COSPCP09): Segments 7, 8 (except for a few tributaries), and 9 were combined into Segment 7, as the uses and standards are the same for all three segments as a result of upgrades to the Aquatic Life use (from Cold 2 to Cold 1) on Segment 8. Segment 7 has CS-II temperature standards. Some Segment 8 tributaries (Middle Fork Rabbit Creek, Stonewall Creek, North Fork Lone Pine Creek, and South Fork Lone Pine Creek, including all tributaries and wetlands) remained in Segment 8 to facilitate changing the Aquatic Life use from Cold 2 to Cold 1 and the temperature standards from CS-II to CS-I. As a result of these changes, Segment 9 is now vacant (shown as "Deleted." in Appendix 38-1).
Cache la Poudre segments 11 and 12 (COSPCP11 and COSPCP12): Modifications were made to segments 11 and 12 to facilitate changes to the Aquatic Life use and temperature standards on a portion of Segment 11, and to add a Water Supply use to Segment 11 and a portion of Segment 12. The boundary between segments 11 and 12 was moved upstream, and Segment 12 was divided into segments 12a and 12b.
The portion of the mainstem of the Cache la Poudre River from Shields Street in Fort Collins to Prospect Road (40.567159, -105.027237) in Fort Collins remained in Segment 11 and the Aquatic Life use was changed from Warm 1 to Cold 1, the temperature standards were changed from WS-I to CS-II, and a Water Supply use was added. The portion of Segment 11 from Prospect Road to the confluence with Boxelder Creek was moved to the next downstream segment (Segment 12) to facilitate retention of the existing Aquatic Life Warm 1 use and WS-I temperature standards. As a result of this move, the upstream boundary of Segment 12 was moved approximately 2.75 miles upstream from Boxelder Creek to Prospect Road.
Segment 12 was divided into 12a and 12b to facilitate adoption of the Water Supply use on the upper portion of the segment. Segment 12a includes the mainstem of the Cache la Poudre River from Prospect Road to U.S. Hwy 85 (40.423323, -104.678956) in Greeley and has a Water Supply use. Segment 12b includes the portion of the Cache la Poudre River from U.S. Hwy 85 to the confluence with the South Platte River and was not assigned a Water Supply use.
In summary, Segment 11 (from Shields Street to Prospect Road) now has Aquatic Life Cold 1 and Water Supply uses, Segment 12a (Prospect Road to U.S. Hwy 85) remains Aquatic Life Warm 1 and a Water Supply use was added, and for Segment 12b no use classification changes were adopted.
Cache la Poudre segments 13b and 13c (COSPCP13b and COSPCP13c): The mainstem of Boxelder Creek from the source to above Slab Canyon Wash was moved from Segment 13b to Segment 13c to facilitate changing the Aquatic Life use from Warm to Cold. Segments 13b and 13c were then switched so that the segments were ordered from upstream to downstream. New Segment 13b contains Boxelder Creek from the source to Slab Canyon Wash, and the mainstems of South Branch of Boxelder Creek, Northern Branch of Boxelder Creek, and Sand Creek. New Segment 13c contains of Boxelder Creek from Slab Canyon to the confluence of the Cache la Poudre River.
Lower South Platte Segment 1 (COSPLS01): Segment 1 was split into segments 1a and 1b. Segment 1a includes the South Platte River from the Weld/Morgan County line to the Morgan/Washington County line. Segment 1b includes the South Platte River from the Morgan/Washington County line to the Colorado/Nebraska border. This resegmentation facilitates changing the Aquatic Life use from Warm 2 to Warm 1 and the temperature standards from WS-II to WS-I on Segment 1a.
Lower South Platte segments 2a and 2b (COSPLS02a and COSPLS02b): Segments 2a and 2b were combined into new Segment 2, as the uses and standards are the same for both segments as a result of upgrades to the Aquatic Life use (from Warm 2 to Warm 1) on both segments and the Recreation use (from P to E) on Segment 2a, and the addition of the Water Supply use on Segment 2b. The segment description for Segment 2 is the same as Segment 2a, except it no longer has an exception for Segment 2b.
Lower South Platte Segment 3 (COSPLS03) and Middle South Platte Segment 8 (COSPMS08): Riverside Reservoir was moved from Lower South Platte Segment 3 to new Middle South Platte Segment 8. This change was made because Riverside Reservoir is actually in the Middle South Platte sub-basin.
Lower South Platte segments 4 and 5 (COSPLS04 and COSPLS05): Segments 4 and 5 were combined into Segment 4, as the uses and standards are the same for both segments as a result of application of the full suite of Aquatic Life standards on Segment 4 and an upgrade of the Recreation use (from P to E) on Segment 4. The segment description for Segment 4 was changed to eliminate the exception for Segment 5. Segment 5 was deleted.
Republican River segments 8 and 9 (COSPRE08 and COSPRE09): Segments 8 and 9 were combined into Segment 8, as the uses and standards are the same for both segments as a result of application of the full suite of Aquatic Life standards and upgrades to the Aquatic Life use (from Warm 2 to Warm 1) and Recreation use (from U to E) on Segment 8. The segment description for Segment 8 was changed to eliminate the exception for Segment 9. Segment 9 was deleted.
Segment descriptions were also edited to improve clarity, correct typographical errors, and correct spelling errors. These changes are listed in Section O.
The commission reviewed information regarding the current Aquatic Life use classifications and evidence pertaining to existing aquatic communities. In addition, newly created segments were given the same Aquatic Life use classification as the segment from which they were split, unless there was evidence to show that the existing use classification was inappropriate.
Some segments assigned an Aquatic Life use classification were missing one or more standards to protect that use. The commission adopted the missing standards for the following segments:
Cherry Creek: 4a (chronic total recoverable iron), 4b (chronic total recoverable iron)
Big Dry Creek: 4b (acute and chronic ammonia), 5a (acute and chronic ammonia), 5b (acute and chronic ammonia)
Lower South Platte River: 2 (full suite of aquatic life use standards), 4 (full suite of aquatic life use standards)
Republican River: 6 (full suite of aquatic life use standards), 7 (full suite of aquatic life use standards), 8 (full suite of aquatic life use standards)
The commission reviewed information regarding the existing aquatic communities. No segments were lacking an Aquatic Life use, but Class 2 segments with high MMI scores (or other metrics indicating a diverse benthic macroinvertebrate community) and/or a wide variety of fish species, including sensitive species, were upgraded from Class 2 to Class 1.
The following segments were upgraded from Cold 2 to Cold 1:
Bear Creek: 1b
Cache la Poudre River: 8, 13b
The following segments were upgraded from Warm 2 to Warm 1:
Upper South Platte River: 15, 16i
Cherry Creek: 1, 3, 7
Clear Creek: 18a
Big Dry Creek: 1
Boulder Creek: 7b, 8, 11
Middle South Platte River: 1a, 1b, 5c
Big Thompson River: 5, 9, 19
Cache la Poudre River: 13a, 13c
Lower South Platte River: 1a, 2
Republican River: 6, 8
Clear Creek Segment 14a (COSPCL14a): The commission did not adopt the division's proposal to upgrade the Aquatic Life use classification on Clear Creek Segment 14a from Warm 2 to Warm 1 based on the evidence in the hearing. Some commissioners were concerned about the evidence regarding the presence of a wide variety of species, and other commissioners determined insufficient recent data were available to support an upgrade of the Aquatic Life use classification at this time.
Big Dry Creek Segment 1 (COSPBD01): While Water + Fish standards are typically applied to all Class 1 Aquatic Life segments which also have a Water Supply classification, the commission declined to apply the fish ingestion portion of the water + fish human health standards on Big Dry Creek segment 1 based on evidence presented that indicated fishing is not taking place on a recurring basis.
The commission reviewed information regarding the existing aquatic communities. For segments where the existing aquatic communities are not aligned with the Aquatic Life use, the following segments were changed from Warm to Cold:
The following segments were upgraded from Warm 1 to Cold 1:
Cache la Poudre River: 11 The following segment was upgraded from Warm 2 to Cold 1:
St. Vrain Creek: 5
The lists above include Aquatic Life use changes that apply to entire segments. Significant differences in the Aquatic Life use that warrant a change on only a portion of a segment are described in Section A (Water Body Segmentation).
The Aquatic Life Warm 1 Goal Qualifier was removed from the following segment because fish and benthic macroinvertebrate data demonstrate a wide variety of biota, including sensitive species, is currently being sustained:
Clear Creek: 15
The commission reviewed all Class 2 segments that have fish that are "of a catchable size and which are normally consumed and where there is evidence that fishing takes place on a recurring basis." Water + Fish or Fish Ingestion standards were applied to the following segments:
Clear Creek: 3b, 13b
Big Dry Creek: 7
Cache la Poudre River: 22
Lower South Platte River: 4
The commission reviewed information regarding the current Recreation use classifications and evidence pertaining to actual or potential primary contact recreation. In addition, newly created segments were given the same Recreation use classification as the segment from which they were split, unless there was evidence to show that the existing use classification was inappropriate. The lists in this section include Recreation use changes that apply to entire segments. Significant differences in the Recreation use that warrant a change on only a portion of a segment are described in Section A (Water Body Segmentation).
Based upon evidence that portions of these segments are publicly accessible and located in a developed area where there is easy access for children, it was determined that primary contact recreation is expected to occur. The following segments with a Recreation P use classification and standards were upgraded to Recreation E:
Big Dry Creek: 1, 4b
Big Thompson River: 5 (changed from seasonal P application to year-round E)
Lower South Platte River: 2, 4
Based upon evidence that portions of these segments are publicly accessible and located in a developed area where there is easy access for children, it was determined that primary contact recreation is expected to occur. The following segments with a Recreation N use classification and standards were upgraded to Recreation E:
Big Dry Creek: 6
Big Thompson River: 3 (changed from seasonal N application to year-round E), 4 (changed from seasonal N application to year-round E), 5 (changed from seasonal N application to year-round E)
Based upon evidence that portions of these segments are publicly accessible and/or accessible to families who live in the area or visitors to public recreation lands in these segments, it was determined that primary contact recreation is expected to occur, including water play by children. The following segments with a Recreation U use classification and standards were upgraded to Recreation E:
Clear Creek: 17b, 24
Republican River: 8
Based upon evidence that portions of these segments are publicly accessible and/or accessible to families who live in the area or visitors to public recreation lands in these segments, it was determined that there is the potential for primary contact recreation, including water play by children. However, at this time, existing primary contact uses were not identified. Therefore, the following segments with a Recreation N use classification and standards were upgraded to Recreation P:
Cache la Poudre River: 13c (changed from seasonal N application to year-round P) Republican River: 7
The commission reviewed information regarding the current Water Supply use classifications and evidence pertaining to potable water supplies. In addition, newly created segments were given the same Water Supply use classification as the segment from which they were split, unless there was evidence to show that the existing use classification was inappropriate. The lists in this section include Water Supply use changes that apply to entire segments. Significant differences in the Water Supply use that warrant a change on only a portion of a segment are described in Section A (Water Body Segmentation).
The commission added a Water Supply use classification and standards where the evidence demonstrated surface waters are used for drinking water and/or there is a reasonable potential for a hydrological connection between surface water and alluvial wells used for drinking water. The Water Supply use classification and standards were added to the following segments:
Upper South Platte River: 11b, 16a, 16e, 16k
Clear Creek: 13b
Big Dry Creek: 1
Boulder Creek: 8
St. Vrain Creek: 3, 6b
Middle South Platte River: 5c
Big Thompson River: 5, 6
Cache la Poudre River: 11, 12a, 13c
Republican River: 4, 6
Cache la Poudre River segments 11 and 12a (COSPCP11 and COSPCP12a): The commission adopted the Water Supply use classification and standards on Cache la Poudre River segments 11 and 12a with a 5 year delayed effective date (12/31/2025) due to the City of Fort Collins and Front Range Energy's challenges related to gathering information regarding the use of existing domestic water supply wells, as well as future uses, due to stay-at-home orders and resource limitations related COVID-19 (Coronavirus Disease 2019).
The commission removed the Water Supply use classification and standards where the evidence demonstrated that a Water Supply use does not currently exist due to flow or other conditions, and that such a use is not reasonably expected in the future due to water rights, source water options, or other conditions. The Water Supply standard for chloride was retained for these segments, given concerns regarding the protection of aquatic life by the existing Water Supply standards. The Water Supply use classification and standards, except for chloride, were removed from the following segments:
Upper South Platte River: 2c
Upper South Platte River Segment 2c (COSPUS02c): The commission removed the Water Supply use classification and standards from South Mosquito Creek, the portion of Mosquito Creek above Road #698 (39.270971, -106.098846), and No Name Creek. Evidence was presented that demonstrated that the Water Supply use does not currently exist, has not existed since 1978, and is not reasonably expected in the future due to the current land zoning and ownership and the significant depth of existing wells.
The commission retained the 250 mg/L chronic (30-day average) standard for chloride as an interim step, based on evidence presented in earlier hearings demonstrating the toxic effects of chloride on aquatic life. Retaining the current chloride standard is necessary to protect the assigned Aquatic Life uses and to ensure that these waters are free from substances that are toxic to aquatic life in accordance with 31.11(1)(a)(iv). The commission retained the numeric standard for chloride because narrative standards have often proved challenging to implement, and interim numeric standards will provide implementable interim standards while allowing time for development of robust replacement criteria based on the latest scientific information.
The commission recognizes that there is scientific uncertainty about the appropriate standards for chloride and/or sulfate to protect the Aquatic Life use, and that appropriate standards may need to recognize that toxicity is affected by site water characteristics (similar to the influence of hardness on the toxicity of dissolved metals). The commission's intention is that future revisions to the numeric standards assigned to this segment, and also to Regulation No. 31 (i.e., aquatic life-based table values chloride and/or sulfate), can be considered if:
The commission reviewed information regarding the current Agriculture use classifications and evidence pertaining to livestock watering and crop irrigation for the three segments lacking an Agriculture use (Clear Creek segments 7a, 7b, and 8). Based on an evaluation of the available data and information, no changes were adopted at this time.
The commission declined to adopt EPA's revised 304(a) Aquatic Life criteria for selenium, ammonia, and aluminum at this time; however, the division is committed to evaluating these new criteria. Studies are currently underway for each parameter to improve understanding of these criteria in the context of water quality conditions in Colorado and how these criteria may be adopted and implemented in Colorado in the future.
EPA has also released updated criteria or guidance for several other parameters, including copper (Aquatic Life), E. coli (Recreation), cyanotoxins (Recreation), and the human health risk exposure assumptions. However, the division does not recommend adopting EPA's recommendations for these parameters at this time, as these items are not included on the division's 10-year water quality roadmap.
The commission reviewed all segments designated Use Protected to determine if the Use Protected designation was still warranted. Based upon available water quality data, the Use Protected designation was upgraded to Reviewable on the following segments:
Boulder Creek: 11
Upper South Platte River Segment 15 (COSPUS15), Middle South Platte River Segment 1a (COSPMS01a), and Clear Creek Segment 15 (COSPCL15): The commission declined to adopt the division's proposal to upgrade the antidegradation classification from Use Protected to Reviewable on Upper South Platte River segment 15 and Middle South Platte River segment 1a. Additionally, the commission changed the antidegradation classification from Reviewable to Use Protected on Clear Creek segment 15. In its proposal to upgrade Upper South Platte River segment 15 and Middle South Platte River segment 1a to reviewable and to maintain Clear Creek segment 15 as reviewable the Division presented evidence and arguments that these segments did not qualify for use protected status under the tests set forth in section 31.8 . Other parties presented evidence and arguments that these segments should be designated as use protected under the tests set forth in section 31.8 and the statutory language, "Use-protected waters shall be those waters with existing quality that is not better than necessary to support propagation of fish, shellfish, and wildlife and recreation in and on the water." CRS 25-8-209(4). Despite the regulatory language, the commission decided that as a matter of policy, due to the unique circumstances and evidence presented in this hearing for these particular segments, it is more consistent with the statutory language for these segments to be classified as Use Protected.
For Upper South Platte River Segment 15 and Middle South Platte River Segment 1a, the commission retained the Use Protected designation based on the weight of the evidence including that the segments receive multiple treated wastewater discharges, aquatic habitat is impacted by flow reductions from multiple manmade diversions, and there was insufficient evidence to demonstrate that existing water quality is better than necessary to support fishable and swimmable uses. For example, in Upper South Platte River Segment 15, water quality exceedances have been observed for E. coli, cadmium (dissolved), ammonia, temperature, and chlorophyll 'a', and Middle South Platte River Segment 1a is currently on the section 303(d) list for E. coli, and water quality standard exceedances have been observed for dissolved oxygen and chlorophyll 'a'.
For Clear Creek Segment 15, the commission changed the antidegradation designation to Use Protected based on the weight of the evidence including that the segments receive multiple treated wastewater discharges, aquatic habitat is impacted by flow reductions from multiple manmade diversions, and the existing water quality is not better than necessary to support fishable and swimmable uses. For example, Clear Creek Segment 15 is currently on the section 303(d) list for organic sediment, temperature, ammonia, and E. coli.
The Commission's policy decision that these segments should be designated Use Protected based on existing quality is substantially influenced by the fact that these segments have been impacted by water quality pollutants for decades. However, the commission also noted that marked improvements in water quality have occurred over time and that improved water quality conditions may warrant reconsideration in the future. The Commission notes that water quality impacts resulting from a spill or other short term water quality condition would present very different circumstances, which the Commission is not addressing in the current action.
Site-specific ambient quality-based standards are adopted where a comprehensive analysis has been conducted demonstrating that ambient water quality levels elevated above the water quality standards are a result of natural conditions or are infeasible to reverse, but are adequate to protect the highest attainable use (31.7(1)(b)(ii)). All existing ambient-based standards were reviewed and no revisions were made.
Cherry Creek Segment 4b (COSPCH04b): During the 2015 Regulation No. 38 rulemaking hearing, the commission adopted site-specific ambient quality-based standards for selenium for Segment 4b and directed Cottonwood Water and Sanitation District (CWSD) to develop a study plan in agreement with stakeholders to collect additional baseline data that would support a "before and after discharge" evaluation of aquatic life. In this rulemaking, CWSD provided an update to the commission regarding the study plan developed and implemented for baseline data collection and describing activities completed since 2015. Given the potential detrimental effect of increased selenium to the downstream Aquatic Life use after discharge from the plant resumed in early 2020, CWSD agreed to a longevity plan that details continued data collection and highest attainable use evaluation activities to support review of the ambient-based standards. The plan includes equivalent or better sampling as the "before" study to demonstrate whether the site-specific standards are appropriate to protect downstream aquatic communities such as the commercially important walleye fishery in Cherry Creek Reservoir. The commission will review these site-specific ambient quality-based standards in the next Regulation No. 38 rulemaking hearing using data collected by CWSD over the next five years to determine if the site-specific standards are still appropriate and protective of the Aquatic Life use in Segment 4b and downstream waters.
Site-specific criteria-based standards are adopted where site-specific studies demonstrate standards other than table value standards are appropriate (31.7(1)(b)(iii)). All existing criteria-based site-specific standards were reviewed, and where appropriate were revised, allowed to expire, or deleted. Site-specific standards were allowed to expire from the following segments:
Clear Creek: 14a (acute and chronic zinc), 14b (acute and chronic zinc), 15 (acute and chronic zinc)
Site-specific copper standards based on the Fixed Monitoring Benchmark (FMB) application of the Biotic Ligand Model (BLM) were adopted for multiple segments during the December 2014 temporary modifications rulemaking (Big Thompson Segment 2) and the June 2015 Regulation No. 38 rulemaking (Upper South Platte segments 14, 15, and 16g and Middle South Platte Segment 1a). When these site-specific standards were adopted, proponents agreed to longevity plans that included continued monitoring and analysis of BLM parameters to facilitate review of the standards at the future basin hearings (38.90(I)).
Using these data, the commission reviewed all segments with BLM-based standards for copper. To determine if water quality conditions had changed significantly and standards revisions were necessary, existing BLM-based standards were compared to BLM-based standards calculated from the more recent datasets using a 95 percent confidence interval approach.
Based on an evaluation of more recent data, BLM-based site-specific copper standards were not revised for the following segments:
Upper South Platte River: 14, 16g
Big Thompson River: 2
Based on an evaluation of more recent data, BLM-based site-specific copper standards were revised for the following segments:
Upper South Platte River: 15
Middle South Platte River: 1a
The commission will review these BLM-based standards in the next Regulation No. 38 rulemaking hearing using data collected over the next five years to ensure that BLM-based standards capture any changes in water quality. Centennial Water and Sanitation District, Metro Wastewater Reclamation District, and Upper Thompson Sanitation District have agreed to longevity plans to continue all necessary data collection and evaluation activities to support review of the BLM-derived copper standards at the next Regulation No. 38 hearing.
All existing temporary modifications were examined to determine whether they should be deleted, modified, extended, or left unchanged.
The commission allowed to expire on 12/31/2020 temporary modifications on the following segments:
Upper South Platte River: 10 (temperature), 15 (chloride, sulfate)
Clear Creek: 7a (cadmium, copper, iron, lead, mercury, nickel, silver, zinc), 7b (cadmium,
copper, iron, lead, mercury, nickel, silver, zinc)
Clear Creek: 13b (temperature)
St. Vrain Creek: 6 (manganese), 7 (iron and manganese)
Big Thompson River: 9 (selenium)
Clear Creek Segment 13b (COSPCL13b): Black Hawk and the Black Hawk - Central City Sanitation District withdrew its proposal to extend the existing temperature temporary modification for Segment 13b based on its agreement with the division, EPA, and CPW that a temporary modification is not the most appropriate regulatory tool to address temperature issues at its treatment facility at this time. Uncertainty remains regarding the appropriate underlying standards and the extent of contributions from natural and irreversible human-induced conditions; however, Black Hawk - Central City Sanitation District currently has no effluent limits for temperature in their permit and may qualify for a compliance schedule for temperature limits when the permit is renewed. In addition, Black Hawk is expected to evaluate whether it may be possible to attain effluent limits based on the current underlying standard. The commission expects that the division will continue to work with Black Hawk and the Black Hawk - Central City Sanitation District regarding the use of appropriate regulatory tools, including temporary modifications or discharger specific variances, as new information becomes available regarding the uncertainties related to temperature on Segment 13b.
St. Vrain segments 6 and 7 (COSPSV06 and COSPSV07): The commission allowed the temporary modifications for manganese on Segment 6 and iron and manganese on Segment 7 to expire on 12/31/2020, as the underlying water quality standards are being attained.
The commission modified the following temporary modifications:
Upper South Platte River: 15, 16g
Clear Creek: 7a (temperature), 7b (temperature)
St. Vrain Creek: 6a
Upper South Platte Segment 15 (COSPUS15): Metro Wastewater Reclamation District proposed a one year extension to the existing "current condition" temporary modification for temperature (expires 12/31/2020, new expiration 12/31/2021). The extension of the temporary modification is based on Metro's information showing continued instream non-attainment of temperature standards and predicted compliance problems with water quality-based effluent limits (WQBELs). Additional time is needed to finish developing a proposal for a discharger specific variance (DSV). Metro has committed to a plan to resolve uncertainty that includes ongoing monitoring and reporting of instream and effluent temperature, as well as providing annual updates to the division in June through the duration of the temporary modification, beginning in 2020 (Metro Exhibit 12).
Upper South Platte Segment 16g (COSPUS16g): Centennial Water & Sanitation District provided an update to the commission regarding progress being made in implementing the existing plan to resolve uncertainty and demonstrating the ongoing need for the temporary modification of the chronic temperature standard (expires 12/31/2020). Centennial presented information that shows continued instream non-attainment of chronic temperature standards, predicted compliance problems with water quality-based effluent limits (WQBELs) during the winter months, and significant uncertainty regarding the appropriate chronic winter temperature standards. Centennial demonstrated the need for an extension of the temporary modification to provide time to complete an alternatives analysis to determine feasible alternatives for controlling temperature at its facility and potentially develop a discharger-specific variance. More time is also needed to collect additional temperature data, characterize the highest attainable Aquatic Life use, potentially participate in temperature standards studies, engage with stakeholders, and review low-cost options to improve water quality. Centennial has committed to providing annual updates to the division each June through the duration of the temporary modification, beginning in 2021, and final results of the alternatives analysis will be provided to the division by June 2023.
Based on this information, the commission adopted an extension of the temporary modification (MWAT = "current condition", 12/1-2/29) with the plan to resolve uncertainty submitted by Centennial (Exhibit 6). The temporary modification applies only for the periods with concurrent instream non-attainment and WQBEL non-compliance (December through February) and expires December 31, 2025. The operative value of the temporary modification is the narrative "current condition." In future reviews of this temporary modification, the commission will use the following values to compare to the most recent five years of representative data to determine if effluent and waterbody quality is maintained and ensure that the existing uses are protected. These values are for use by the commission in future reviews of the temporary modification and are not intended to direct the division's implementation of "current condition" temporary modifications in permits:
Additionally, the commission will consider whether seasonal trends of warming and cooling have been maintained.
Clear Creek segments 7a and 7b (COSPCL07a and COSPCL07b): Climax Molybdenum Company provided an update to the commission regarding progress being made in implementing the existing plan to resolve uncertainty and demonstrating the ongoing need for the temporary modifications for chronic and acute temperature, copper, and zinc; chronic cadmium, iron, lead, mercury, nickel, and silver for Clear Creek segments 7a and 7b that are set to expire 6/30/2023. The commission deleted the temporary modifications for metals based on an evaluation of the available instream and effluent data that demonstrated attainment of the standards instream and the lack of a water quality-based effluent limit (WQBEL) compliance issue.
For temperature, Climax's update demonstrated continued instream nonattainment, predicted compliance issues, and remaining uncertainty regarding the appropriate underlying standards to protect the uses and the extent to which instream conditions are reversible. Climax also provided an updated plan to resolve uncertainty (Exhibit 5) that included details regarding the scheduled investigations and reporting required to resolve the uncertainty by 6/30/2023. Additionally, the temporary modification was narrowed to apply only for the periods with concurrent instream non-attainment and predicted WQBEL non-compliance (MWAT = "current condition", 10/1-11/30 and 4/1-5/31). The operative value of the temporary modification is the narrative "current condition" and the expiration date remains unchanged.
In future reviews of this temporary modification, the commission will use the following values to compare to the most recent five years of representative data to determine if effluent quality is maintained and ensure that the existing uses are protected. These values are for use by the commission in future reviews of the temporary modification and are not intended to direct implementation of "current condition" temporary modifications in permits:
Additionally, the commission will consider whether seasonal trends of warming and cooling have been maintained.
Data to adequately characterize the status quo of the waterbody at the time the temporary modification was originally adopted were not available. It is the commission's expectation that as more data become available to characterize instream waterbody temperature conditions, representative numeric values to represent instream status quo will be determined as soon as possible for the commission's use in future reviews of this temporary modification.
St. Vrain Segment 6a (COSPSV06a): For Segment 6a, the commission extended the "current condition" temporary modification for total recoverable iron from 12/31/2020 to 6/30/2023 to provide time for Raytheon to investigate the sources and characterize the highest attainable use. Raytheon provided an updated plan to resolve uncertainty that includes a detailed timeline for data collection and updates every 6 months to the division and stakeholders (Revised Exhibit 4). The commission determined that a temporary modification continues to be justified based on demonstrated instream non-attainment, uncertainty regarding the underlying standard, demonstrated compliance problems, and a robust plan to resolve the uncertainty and eliminate the need for the temporary modification by 6/30/2023.
The operative value of the temporary modification is the narrative "current condition." The temporary modification for iron was first adopted by the commission in December 2016. Data to characterize the baseline condition when the temporary modification was adopted are available for Seep 1 and Seep 2, and more recent water quality data are available for the site 300 feet downstream of Seep 2. In future reviews of this temporary modification, the commission will use the following values to compare to the most recent five years of representative data to determine if effluent quality is maintained and ensure that the existing uses are protected. These values are for use by the commission in future reviews of the temporary modification and are not intended to direct implementation of "current condition" temporary modifications in permits:
To remain consistent with the commission's decisions regarding arsenic in section 38.99 , all existing temporary modifications for arsenic of "As(ch)=hybrid" (expiration date of 12/31/24) were retained. In addition, for segments where a Water Supply or Aquatic Life use change resulted in a corresponding revision of the arsenic standard, an arsenic temporary modification was adopted for the 0.02 µg/L Water + Fish numeric standard in recognition of existing and predicted compliance issues, instream nonattainment, and the uncertainty regarding the water quality standard necessary to protect current and/or future uses and the extent to which ambient concentrations of arsenic are natural or irreversible (31.7(3)).
The division submitted a plan to resolve uncertainty in the 2019 Temporary Modifications rulemaking. The division plans to propose revised standards for arsenic as soon as possible following updated toxicological information from EPA's Integrated Risk Information System (IRIS) and completion of ongoing studies to better understand arsenic conditions in Colorado. Furthermore, per the conditions of the revised and extended temporary modification at 38.6(2)(c) (effective 6/30/2020 and expires 12/31/2024), and based on the widespread need to make progress to understand sources of arsenic and set forth processes for lowering arsenic in discharges, additional permit Terms and Conditions (T&Cs) are being implemented for facilities benefitting from the "current condition" temporary modification. These T&Cs may include requirements for additional monitoring, source identification, and characterization of source control and treatment options for reducing arsenic concentrations in effluent. The commission recognizes the need to resolve the uncertainty in the arsenic standards and ensure that human health is adequately protected.
Temporary modifications for arsenic were added to the following segments:
Upper South Platte River: 11a, 15, 16i, 16k
Cherry Creek: 1, 3, 4b, 7
Clear Creek: 13b, 18a
Boulder Creek: 7b, 8, 11
St. Vrain Creek: 3, 5, 6b
Big Thompson River: 5, 6, 9
Cache la Poudre River: 13a, 13b, 13c
Lower South Platte River: 2
Republican River: 4, 6
As a result of a change to the underlying arsenic standard due to removal of the Water Supply use, the temporary modification for arsenic is no longer needed and was removed from the following segment:
Upper South Platte River: 2c
There is currently one discharger specific variance (DSV) for selenium which applies to two segments (Upper South Platte segments 15 and 16i). The commission reviewed the basis for this DSV and the available information regarding Suncor Energy (U.S.A.) Inc.'s progress toward achieving the alternate effluent limit. The commission determined that the alternative effluent Limit (AEL) adopted in 2016 continues to represent the highest attainable water quality that is feasible for Suncor to achieve. Therefore, the commission determined that this DSV is still appropriate and does not require revision at this time.
The commission revised temperature criteria in Regulation No. 31 in 2007, and again in 2010, based on the development of the Colorado Temperature Database and a lengthy stakeholder process. In 2015, the new temperature standards were adopted for all segments with an Aquatic Life use classification in Regulation No. 38. In June 2016, temperature criteria in Regulation No. 31 were further revised, including changes to the temperature table value standards, revision of warm water winter acute standards, and the addition of footnotes to protect lake trout and mountain whitefish.
While early life stages of mountain whitefish are known to be the most thermally-sensitive, the time period these early life stages occur can vary from site to site. Mountain whitefish spawn in the fall, but timing of spawning, incubation, and emergence all depend on a variety of site-specific factors, including water temperature. The incubation period takes longer when water is colder, and that will delay hatching, emergence, and migration of fry. Depending on when spawning occurs and the water temperature in which the eggs are spawned and incubated, the incubation period could last through late spring.
Based on information provided by CPW, thermally-sensitive early life stages of mountain whitefish occur in certain water bodies in Regulation No. 38. Spawning begins in October and the fry life stage is complete by May in these water bodies. Therefore, only limited application of the mountain whitefish summer temperature standards to protect eggs, larvae, and fry is necessary.
In segments currently assigned CS-I temperature standards, the application of the mountain whitefish summer temperature standards is not necessary. The winter season included in CS-I temperature standards (i.e., October to May) is expected to cover the period when mountain whitefish early life stages are expected to occur (i.e., October to May). In addition, the CS-I winter standards are more stringent than the mountain whitefish summer standards. Therefore, because the CS-I temperature standards are protective of mountain whitefish early life stages, the commission did not adopt the mountain whitefish summer standards on segments with CS-I temperature standards. While the commission made no changes to the temperature standards, mountain whitefish spawning and early life stages are known to occur in the following CS-I segment:
Cache la Poudre River: 2a
In this hearing, the commission adopted standards to protect lake trout on a site-specific basis where information provided by CPW indicated that this species occurs and protection from thermal impacts is appropriate. Adoption of lake trout standards is dependent on two factors: the existing temperature tier (cold lake or cold large lake) and whether a site-specific temperature standard was already in place. For cold lakes, only the chronic lake trout standard was adopted, as the acute cold lake temperature standard (21.2°C) is more protective than the acute lake trout standard (22.4°C). The chronic lake trout standard (16.6°C) is more protective than the chronic cold lake temperature standard (17.0°C). For cold large lakes, both acute and chronic lake trout standards were adopted unless there was a site-specific standard in place. Acute and chronic lake trout standards (22.4 and 16.6°C, respectively) are more protective than acute and chronic cold large lake standards (24.2 and 18.3°C, respectively). Lake trout standards were not proposed where an existing site-specific standard is applied.
Temperature standards to protect lake trout were applied to the following segments:
Upper South Platte River: 19 (Jefferson Lake DM and MWAT)
Clear Creek: 21 (Chase Gulch Reservoir MWAT)
Boulder Creek: 14 (Barker Reservoir MWAT), 18 (Gross Reservoir DM)
Big Thompson River: 11 (Carter Reservoir DM)
Cache la Poudre River: 18 (Barnes Meadow Reservoir MWAT; Chambers Lake DM and MWAT)
Regulation No. 31 in 2007, the division and others have worked to ensure that appropriate temperature standards were adopted for segments throughout the state. At times, this effort to assign temperature standards has also included reevaluation of the existing Aquatic Life use classifications, and use revisions have been proposed and adopted where appropriate. Incremental progress continues as temperature standards are refined based on the experience and data gains that have occurred since initial adoption of temperature standards.
In the 2016 Regulation No. 31 hearing, the commission declined to adopt the division's proposal for statewide solutions for temperature transition zones and shoulder seasons, in favor of a basin-by-basin consideration of temperature standards on a site-specific basis. The basin-by-basin approach was selected as it allows for consideration of temperature attainability and ambient quality-based site-specific temperature standards issues in the context of multiple lines of evidence and site-specific contravening evidence. The sections below describe the considerations and methods used to develop and support the site-specific temperature standards revisions adopted in this basin hearing.
Temperature standards have been implemented and reviewed in Regulation No. 38 during three triennial reviews - 2009, 2015, and 2020. The level of emphasis and effort dedicated to understanding the aquatic community and temperature standards implementation during these reviews has resulted in a great deal of progress and application of appropriate temperature standards across the basin. Accordingly, no site-specific temperature standards and fewer Aquatic Life use revisions were necessary compared to previous basin reviews.
Based upon a review of information regarding the species expected to occur, temperature data, physical habitat, land cover/use, groundwater inputs, flow conditions, and all other available information regarding thermal drivers, no segments were identified as warranting a change to less stringent temperature standards as a result of water quality that is not feasible to improve or where the thermal regime is the result of natural conditions, but is sufficient to protect the highest attainable use.
Based upon information regarding the species expected to occur, the commission adopted revisions of temperature standards to protect thermally-sensitive species for the segments listed below.
The following segments were changed from CS-II to CS-I:
Cache la Poudre River: 3, 8
The following segments were changed from WS-I to CS-II:
St. Vrain Creek: 5
Cache la Poudre River: 11
Cache la Poudre Segment 11 (COSPCP11): Based on fish data collected by various entities and provided to the division by CPW that show the presence of cold water species, including reproducing brown trout and longnose sucker, the commission changed the Aquatic Life use from Warm 1 to Cold 1 and temperature standards from Warm Stream Tier I to Cold Stream Tier II (CS-II). Northern Colorado Water Conservancy District and the City of Fort Collins opposed this change due to uncertainty regarding the attainability of CS-II table value standards in this segment and their intent to pursue site-specific temperature standards at a later hearing. Adoption of CS-II temperature standards to protect the existing Aquatic Life use is necessary and appropriate; however, site-specific refinements may be warranted as additional information and analyses become available regarding the highest attainable Aquatic Life use and feasible temperature control. The commission appreciates the work of the Cache la Poudre Transition Zone work group and supports its continued work. It is the commission's intent that the division will continue to work with interested parties, through the existing Cache la Poudre Transition Zone workgroup and other relevant forums, to determine whether site-specific standards, such as feasibility-based ambient standards or criteria-based standards, are appropriate for this segment, and/or if a compliance schedule or discharger specific variance(s) is appropriate for dischargers to Segment 11 such as Fort Collins.
The following segments were changed from WS-II to WS-I:
Boulder Creek: 7b
Middle South Platte River: 1a, 1b
Cache la Poudre River: 13c
Lower South Platte River: 1a
Further investigation of the appropriate temperature standards is needed, so no changes were adopted at this time for the following segments:
Clear Creek: 14a, 14b, and 15
Clear Creek segments 14a, 14b, and 15 (COSPCL14a, COSPCL14b, COSPCL15): These segments are currently assigned Warm Stream Tier II temperature standards. However, the commission recognizes that there is uncertainty about the appropriate temperature standards applied to these segments based on fish data available from CPW for Clear Creek segments 14a and 15 that show the presence of several cold water species, including consistent catches of large numbers of brown trout and longnose suckers, and occasional catches of rainbow trout, and single-year catches of brook trout and cutthroat trout. Reproduction of cold water species has not been investigated in any of these segments. No fish data are available for Segment 14b, which is a short segment located between segments 14a and 15. These data raise questions regarding the appropriateness of the Warm Stream Tier II temperature standards for these segments. It is the commission's intent that the division will continue to work with CPW and interested parties to resolve the uncertainty regarding whether these populations are self-sustaining, and to what degree the drop structure at the most upstream portion of Segment 14a is obstructing upstream return of cold water fish flushed downstream.
In the March 2012 rulemaking hearing, the commission adopted a sub-classification of the Domestic Water Supply Use called "Direct Use Water Supply Lakes and Reservoirs Sub-classification" (DUWS), in Regulation No. 31, at 31.13(1)(d)(i). This sub-classification is for Water Supply lakes and reservoirs where there is a plant intake location in the lake or reservoir or a man-made conveyance from the lake or reservoir that is used regularly to provide raw water directly to a water treatment plant that treats and disinfects raw water. The commission began to apply this sub-classification in 2013 and anticipated that it would take several basin reviews to evaluate all the reservoirs in the basin. The commission adopted the DUWS sub-classification on the following reservoirs and added "DUWS" to the classification column in the standards tables:
Upper South Platte River: 19 (Woodland Park Reservoir), 22a (Marshall Reservoir)
Cherry Creek: 7 (Rueter-Hess Reservoir)
Clear Creek: 21 (Hole in the Ground Reservoir, Chase Gulch Reservoir, Beaver Brook Reservoir No. 2)
Big Dry Creek: 7 (Welton Reservoir)
Boulder Creek: 17 (Goosehaven Reservoir, Erie Lake, Twomile Canyon Reservoir)
Big Thompson River: 16 (Mirror Lake) and 17 (Pinewood Lake)
The following edits were made to the regulation and Appendix 38-1 to improve clarity and correct typographical errors:
* The formatting of the tables in Appendix 38-1 was modified to include only parameters that have been adopted in a majority of segments. The tables include rows for physical and biological, inorganic, and metals for all parameters which the commission commonly adopts into segments. In segments where there is no numeric standard for a commonly adopted parameter, a blank row for that parameter is included to show the commission's site-specific decision not to adopt a numeric standard for that parameter. The commission removed beryllium and aluminum from all segments where no standard has been adopted because these parameters have only been adopted on a site-specific basis, rather than basin-wide.
* Information was added at 38.6(5) specifying that the mercury standards apply to the total recoverable fraction of all forms, both organic and inorganic, of mercury in water.
* Information was added at 38.6(5) specifying that the ammonia, nitrate, and nitrate standards are to be reported as nitrogen. This is consistent with the description of the standards as they are included in Table II of Regulation No. 31.
* Information regarding site-specific ammonia and dissolved oxygen standards previously adopted for Upper South Platte Segment 15 and Middle South Platte Segment 1a was moved from Appendix 38-1 to 38.6(4) and edited for clarity.
* Information regarding site-specific radionuclide standards previously adopted for Big Dry segments 2, 3, 4a, 4b, 5 was moved from Appendix 38-1 to 38.6(4) and edited for clarity.
* Some segments that were previously deleted, but were reserved as placeholders in Appendix 38-1, were permanently removed from the appendix. Previously-deleted segments that are necessary to maintain continuous numbering of segments were retained. The following previously-deleted segments were not necessary to maintain continuous numbering of segments, and were removed from Appendix 38-1:
Upper South Platte River: US06c, US10b
Bear Creek: 4b and 4c
* Existing site-specific temperature standards were reformatted in the tables to provide clarity and consistency for the following segments:
Upper South Platte River: 6b, 19
Bear Creek: 1b, 1c, 1e
Boulder Creek: 18
Big Thompson River: 11
Cache la Poudre River: 14, 20
Lower South Platte River: 3
* The segment descriptions in Appendix 38-1 were reviewed, and minor revisions were made to several segments to correct grammar, punctuation, and typos, and improve sentence structure. The purpose of these changes was to improve clarity and consistency of the segment descriptions.
Upper South Platte River: 2a, 3, 4, 7, 8, 11b, 16c, 19, 21, 22a, 23
Cherry Creek: 4a
Bear Creek: 3, 6a,11
Clear Creek: 2a, 2b, 2c, 3a, 6, 10, 13b, 16b, 21, 24
Big Dry Creek: 1, 4a, 4b, 5a, 7
Middle South Platte River: 3a, 5c
Big Thompson River: 2, 3, 4, 19
Cache la Poudre River: 1, 6, 7, 13a, 18, 21
Laramie River: 2a, 4
Lower South Platte River: 3, 4
Republican River: 1, 3, 6, 8
* Coordinates were added to several segment descriptions to facilitate location of segment boundaries.
Upper South Platte River: 16d, 16e, 16f
Big Thompson River: 2, 3, 6, 8, 9, 10, 16, 17, 18, 19
Cache la Poudre River: 2b, 10a, 10b, 13a, 16, 18, 21
* Bear Creek Segment 7: The effective date of 12/31/2020 for phosphorus(chronic) was deleted from the 'Other' column, as the standard will be effective on the effective date of this regulation.
* Cherry Creek segments 1, 4a, and 4b: The effective date of 12/31/2020 for phosphorus(chronic) was deleted from the 'Other' column, as the standard will be effective on the effective date of this regulation.
* Clear Creek Segment 12a: Added missing footnote "A" that accompanies Arsenic(T) standard of 0.02-10 µg/L.
* Clear Creek Segment 12b: The designation for the 0.02 µg/L arsenic standard for Water Supply was changed from arsenic to arsenic(T) to reflect the correct fraction of arsenic protective of the use.
* Clear Creek Segment 16b: The exception for Segment 17a was removed. Segment 17a is a lakes and reservoirs segment, while Segment 16b is a stream segment.
* Big Dry segments 2, 4a, 4b, 5a, and 5b: The beryllium standards were changed from beryllium to beryllium(T) to reflect the correct fraction of beryllium that is protective of the use.
* Big Thompson Segment 1: The exception of Segment 2 was unnecessary and was deleted for clarity.
* Big Thompson Segment 6: Exceptions were for segments 7 through 10 were added for clarity.
* Big Thompson Segment 17: Exceptions for segments 18 and 19 were added for clarity.
* Cache la Poudre Segment 2b: An exception for Segment 1 was added for clarity.
5 CCR 1002-38.101